Why are two different types of traditional Japanese knives for fish and vegetables?

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*Borrowing image for the sake of simplicity.

Before Tokyo became the capital of Japan, the emperor and nobles resided in the Kansai region while the shogun lived in the Kanto region. Kansai cuisine is more refined and lighter to suit the nobility, while the flavors in Kanto were stronger for hard working laborers. Due to the class separation in this matter, the nobility in Kansai looked down and mocked those in Kanto. The animosity led to chef in Kanto to not want to use the same tools, which led to the creation of the takobiki and usuba knives that are popularly used today.

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Kansai knives on the left: yanagi and kamagata usuba
Kanto knives on the right: takobiki and usuba

Although, class separation through regions no longer exists, the most prominent difference between the Kanto and Kansai region that can still be seen today lies in the cuisine. You can still find these vast flavor differences by simply tasting the soy sauce; the soy sauce in Kanto is much saltier and stronger than in Kansai. Other popular dishes such as tempura are served with salt instead of a soy sauce based dips.

Mr. Sugai always tells me about his adventures to sushi restaurants in the Kansai region, and how people there donít eat sushi with soy sauce. Apparently, he doesnít like asking for soy sauce since chefs tend to be surprised, but he usually ends up asking anyways. He acknowledges that Kansai cuisine is much more delicate, refined and higher level, but he prefers the saltier foods of the Kanto region since he was raised there. Me on the other hand, I like Kansai cuisine better. :)

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Tempura served with very fine salt

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Sashimi served at Ryuuzanpaku in Kyoto